Two-Dimensional Maps ( map2 )

Definition

An instance M of the parameterized data type map2<I1,I2,E> is an injective mapping from the pairs in I1 x I2, called the index type of M, to the set of variables of data type E, called the element type of M. I must be a pointer, item, or handle type or the type int. We use M(i, j) to denote the variable indexed by (i, j) and we use dom(M) to denote the set of ``used indices''. This set is empty at the time of creation and is modified by map2 accesses.

Related data types are map, d_arrays, h_arrays, and dictionaries.

#include < LEDA/core/map2.h >

Types

map2<I1,I2,E>::item	the item type.
map2<I1,I2,E>::index_type1	the first index type.
map2<I1,I2,E>::index_type2	the second index type .
map2<I1,I2,E>::element_type	the element type.

Creation

map2<I1,I2,E>	M	creates an injective function m from I1 x I2 to the set of unused variables of type E, sets xdef to the default value of type E (if E has no default value then xdef stays undefined) and dom(M) to the empty set, and initializes M with m.
map2<I1,I2,E>	M(E x)	creates an injective function m from I1 x I2 to the set of unused variables of type E, sets xdef to x and dom(M) to the empty set, and initializes M with m.

Operations

E&	M(const I1& i, const I2& j)
		returns the variable M(i).
bool	M.defined(const I1& i, const I2& j)
		returns true if i $\in$ dom(M) and false otherwise.
void	M.clear()	clears M by making dom(M) the empty set.

Implementation

Maps are implemented by hashing with chaining and table doubling. Access operations M(i, j) take expected time O(1).